Search

Objective: In this work we evaluated the bone-forming potential of BMP4, TGFβ1 and BMP4/TGFβ1 mixed by performing histological and morphometric analysis. We also evaluated the immunolabelling of fibronectin (FN) and collagen type III (Col III), two determinant proteins for the early phase of bone repair., Design: Histological, histomorphometric and immunohistochemistry analysis were used to evaluate new bone and blood vessels formation as well as fibronectin and collagen type III expression. 112 male Wistar rats weighing 250-300g had their maxillary second molar extracted. Sockets filled with blood clot (BC) or treated with L (empty liposome), P (PBS), BP (BMP-4 in PBS) and TP (TGF-β1 in PBS), as well as with BL (BMP-4 in liposome) and TL (TGF-β1 in liposome) administered isolated or in association (BTL) were obtained. The animals were sacrificed at 3, 7, 14 and 21 days after surgery., Results: An increased percentage of bone trabeculae, and a higher number of blood vessels were observed in groups BL or TL administered isolated or in association when compared to groups BC, L, P, BP and TP. Fibronectin and collagen type III analysis revealed enhanced expression firstly detected at 3 days followed by a peak at 7 days. Lower levels of immunoreactivity were observed in the sockets filled with blood clot, and treated with L, P, BP and TP when compared with sockets from groups BL, TL and BTL., Conclusion: The present study indicates growth factors carried by liposomes, either in isolated or associated forms, as successful enhancers of the healing process in rat tooth sockets. We also conclude that the expression of fibronectin and collagen type III increases during the early phases of bone repair., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Objective: Intensive mechanical stress and/or inflammation are known to induce alveolar bone resorption. This study investigated whether a distribution of mechanical stress would reduce residual ridge resorption or improve ischaemia., Design: Thirty rats were divided into six experimental groups (n=5). The control group received no intentional stimulation, but rats in the experimental groups wore denture stimulators made of acrylic resin or a soft lining material. The stimulator transmitted masticatory pressure to the rats' palates for four weeks. The four types of soft lining materials investigated in this study dispersed the applied pressure, with compressive stress ranging from 20.8 to 90.8kPa. Volumes of blood flow and bone resorption of denture foundations were measured every week for 4 weeks. Statistical evaluation of these results was performed using two-way ANOVA and Holm-Sidak test within 5% error limits., Results: Non-viscoelastic material clearly induced bone resorption and ischaemia of denture foundations, while viscoelastic materials reduced these phenomena to different extents according to their viscoelastic properties. Ischaemia in the alveolar ridge preceded residual ridge resorption, because the amount of residual ridge resorption and blood flow rate showed a simple linear regression., Conclusion: Animal model of this study suggested that a distribution or reduction of mechanical stress could improve blood flow and decrease alveolar ridge resorption., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Objective: To characterise the 5-hydroxytryptamine (5-HT) receptor subtypes mediating contraction of the inferior alveolar artery. Additionally, to determine the role of cyclooxygenase products, nitric oxide, endothelium, monoamine oxidase and 5-HT uptake in modulating contraction of inferior alveolar arteries to 5-HT., Methods: Contractile responses to 5-HT were examined in vitro using ring segments of bovine inferior alveolar arteries. Affinity constants (K(B)'s) of subtype-selective 5-HT receptor antagonists were determined to characterise the 5-HT receptor-subtypes causing contraction of inferior alveolar arteries., Results: In 100 nM ketanserin or 30 nM spiperone, 5-HT caused a biphasic contraction best-fit by a two-site curve model, where one site was antagonist-sensitive and the other site antagonist-insensitive. 5-HT(2A) receptor-subtype selective antagonists, ketanserin and spiperone, blocked 5-HT induced contraction with K(B)'s of 1.0 and 0.16 nM, respectively. RS102221 (5-HT(2C) selective) and (S)-WAY100135 (5-HT(1A) selective) blocked 5-HT stimulated contraction with low affinities (K(B)'s=100 nM and 330 nM, respectively). GR55562, a 5-HT(1) receptor subtype antagonist with a reported affinity of 500 nM at the 5-HT(1D) receptor subtype, blocked 5-HT induced contraction with a K(B) of 470 nM. Cylooxygenase inhibition with 50 microM ibuprofen caused a 44% increase in maximal contraction to 5-HT; whereas, nitric oxide inhibition with N(G)-nitro-L-arginine, endothelium removal or inhibition of 5-HT uptake and monoamine oxidase with imipramine and iproniazid, respectively, did not affect 5-HT contraction., Conclusions: Both 5-HT(2A) and 5-HT(1D/1B) receptor subtypes mediate 5-HT induced contraction of the bovine inferior alveolar artery. 5-HT stimulated contraction of the inferior alveolar artery is modulated by a vasodilator prostaglandin.

Angiography is often used to investigate age-related changes in the inferior alveolar artery, the major nutrient artery of the mandible. Although histological examinations have been made from several viewpoints, e.g. age change, pathogenesis of osteoradionecrosis, and relation to tooth extraction, these studies have used a limited number of samples and simple histometric methods. The purpose here was to describe histopathological and histomorphometric age-related changes, and to investigate the relation between dentate status and the histomorphometry of the artery. Inferior alveolar arteries from 162 autopsy cases (age range 3-86 years) were examined histometrically with a mathematically standardized method. Histologically, there was diffuse fibrous intimal thickening, but no atheroma formation. Histometric analyses revealed a very gradual increase in both the radius of the artery and the thickness of the media with age, but the luminal radius did not correlate with age. Intimal thickness increased exponentially with age with very different features from those of the increase in the media. The relative radius of the lumen decreased with age after the sixth decade; this is thought to be an index for senile changes in the artery. Among the variables of arterial architecture examined, no particular difference was found between the dentate and non-dentate cases in the molar region.

This study describes the precise determination of the extrusive force in the rat mandibular incisor measured for a relatively longer period of time under artificial respiration with halothane anaesthesia. Following restraint of the eruptive movement of the incisor for a period of 20 h, the pushing force increased gradually and was maintained as an extremely gentle slope toward the end of the experimental period. The maximum pushing forces were estimated to be 9.1 +/- 2.5 (SD) mN in impeded incisors and 9.8 +/- 2.3 mN in unimpeded incisors. When force was converted to pressure, values were 30 +/- 8 (SD)mmHg and 32 +/- 8 mmHg, respectively; the difference was not significant. The maximum pushing force decreased rapidly--almost in parallel--with the fall of systemic arterial blood pressure after death of the animals; the amounts of reduction were 7.2 +/- 1.8 mN (24 +/- 6 mmHg) in impeded incisors and 7.0 +/- 2.0 mN (23 +/- 7 mmHg) in unimpeded incisors. Residual pushing forces were 1.7 +/- 1.0 mN (5.6 +/- 3.3 mmHg) in impeded incisors and 2.5 +/- 0.6 mN (8.2 +/- 2.0 mmHg) in unimpeded incisors; the difference was significant (P < 0.05). These results suggest that, under these experimental conditions, the pushing force of the rat incisor originates primarily from localized blood pressure within the incisor socket and, in part, from tissue growth.

The distribution of nerve fibres immunoreactive to calcitonin gene-related peptide (CGRP), substance P (SP) and neuropeptide Y (NPY) was compared to the general neurochemical markers for nerves and neuroendocrine cells protein gene product 9.5 (PGP 9.5) and neurone-specific enolase (NSE), by use of the avidin-biotin peroxidase complex method in developing dental structures in rats aged 13 to 27 days. A substantially greater part of the nerve fibres was immunoreactive to CGRP and SP than to NPY. In the bell stage, nerve fibres immunoreactive to PGP 9.5, CGRP and SP were found in the dental follicle but not in the dental papilla and stellate reticulum. In the advanced bell stage, after initiation of dentine and enamel formation, PGP 9.5, CGRP- and SP-immunoreactive fibres were found in the dental papilla, while the first NPY-immunoreactive fibres were observed in the papilla when root formation started. Concomitant with the beginning of root development, a subodontoblastic nerve plexus was gradually formed and PGP 9.5-, CGRP- and SP-immunoreactive fibres were found within the dentinal tubules. From the start of root formation, CGRP-, SP- and NPY-immunoreactive nerves were shown in the developing periodontal ligament, although a mature distribution pattern was not observed until root formation was nearly completed. Ameloblasts, odontoblasts and cell-like structures in the outer enamel epithelium and within the dental lamina were PGP 9.5-immunoreactive at the bell stage. As the tooth matured, the immunolabelling gradually decreased, but was still present in some odontoblasts after tooth eruption. NSE-immunoreactive, cell-like structures were found in the periphery of the dental follicle, and persisted close to alveolar bone in the periodontal ligament when the tooth reached occlusion. Hence, it may be concluded that sensory nerves containing SP and CGRP are present in the pulp in advance of sympathetic nerves immunoreactive to NPY.

The distribution of VIP- and CGRP-containing nerve fibres was examined by indirect immunofluorescence. There were many such fibres in the lower third of the ligament, some around the blood vessel close to the socket wall. In the middle third of the ligament, some CGRP-containing fibers entered from the lateral wall of the socket; this type of fibre was more numerous in the lower third than in middle third. There were some VIP-containing fibres but no CGRP-containing fibres in the ligament surrounding the furcation of the molar roots.